JPH0313831B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a single-stone transistor inverter device.

(Prior art) In order to improve the turn-on characteristics of the transistor, an LC series resonant circuit is provided in the base circuit of the switching transistor in a single-stone blocking oscillation type inverter used in a discharge lamp lighting device, etc. (for example, JP-A-58 170364), it has been found that there is a drawback that switching loss occurs during turn-on.

Figure 2 shows the main parts of such a conventional circuit array, where N1 is the input winding of the inverter transformer, Tr is the transistor that switches the input of the input winding N1, and L is the base of the transistor Tr. A connected inductor, N2, is magnetically coupled to the input winding N1 and at its output connects to the transistor.
A control winding that controls on/off of the Tr, C0 is a capacitor, and Rd is a damping resistance of the inductor L. The inductor L and the capacitor C0
and form a series resonant circuit of the base circuit.
C2 is a resonant capacitor that forms a parallel resonant circuit with the input winding N1, etc., and R1 is a starting resistor.

In such an inverter device, the inductor L
The series resonant circuit of the capacitor C0 and the capacitor C0 has the effect of rapidly turning off the capacitor C0.

But for turn-off, the transistor
A polarity voltage VN2 that biases the transistor Tr to the control winding N2 before the Tr off period ends.
occurs, and as a result, a base current Ib as shown in Figure 3c flows through the collector current Ic of the transistor Tr, resulting in a whisker-shaped collector current as shown in Figure 3a.
It was found that Ic1 was generated and caused switching loss.

As a countermeasure for this, if a capacitor Ct is connected between the base and emitter as shown in the second figure, the base current that causes the whisker-shaped current Ic1 is bypassed to this capacitor Ct, and the whisker-shaped current Ic1 is can be prevented from occurring.

(Problem to be Solved by the Invention) However, on the other hand, since the capacitor Ct has a low impedance during turn-off, the carrier extraction from the base becomes difficult, and when the collector current Ic falls, Ic2 shown in Fig. 3 occurs, which causes a switch failure. It had the disadvantage of causing long-term loss.

The present invention has been made in order to solve the problems of the prior art described above, and an object of the present invention is to provide an efficient transistor inverter device by reducing switching loss when turning on and turning off a transistor. It is something.

[Structure of the Invention] (Means for Solving the Problems) The present invention improves the turn-off characteristics of the transistor by providing a series circuit of an inductor and a capacitor in the base circuit of the transistor that turns on and off the input to the input winding. In addition,
A snubber circuit comprising a capacitor and a diode connected in series with each other and a resistor connected in parallel to the diode is provided between the base and emitter of the transistor, and the polarity of the diode is the same as the polarity of the base and emitter of the transistor. The feature of the structure is that it is provided so that

(Function) Regarding the function of the present invention, first, the time when the transistor is turned off will be explained. Even if a voltage is generated in the control winding in the bias direction during the final part of the transistor's off period, the base current that attempts to flow at this voltage is bypassed by the capacitor and diode of the snubber circuit. The transistor will not turn on undesirably.
Then, when the timing for turning on the transistor comes, the base current is supplied to the transistor without being bypassed by the snubber circuit, and the transistor is turned on. Of course, the constants of the snubber circuit are set in advance in accordance with the timing.

Next, the turn-off time will be explained. Due to the action of the series resonant circuit provided in the base circuit of the transistor, a current flows in the drawing direction between the base and emitter of the transistor, but in the present invention, the series circuit of the capacitor and resistor of the snubber circuit is Since it has a higher impedance than a capacitor alone, it has no or little adverse effect on the extraction. Therefore, the fall characteristics of the collector current at turn-off are good. The energy stored in the inductor of the series resonant circuit is damped by the resistor and capacitor of the snubber circuit during the off period of the transistor.

(Example) An example of the present invention will be described below with reference to FIG. In Figure 1, D1 and C1 are rectifiers and capacitors that rectify and smooth the AC power supply, N1 is the input winding of the inverter transformer T, C2 is a resonance capacitor connected in parallel to the input winding N1, Tr is a transistor, and N2 is the control winding of the transistor Tr,
D2 is a reverse current prevention diode connected between the control winding N2 and the emitter of the transistor Tr, C0 and L are a capacitor and inductor forming a series resonant circuit of the base circuit, R1 is a starting resistor, R2, D4 is a resistor and diode forming a discharge circuit for capacitor C0, N3 is an output winding of inverter transformer T, and La is a discharge lamp as a load.

In the circuit described above, a capacitor C3 in series between the base of the transistor Tr and the control winding N2;
A resistor R3 and a diode D3 parallel to this resistor R3.
A snubber circuit consisting of is connected so that the polarity of the diode D3 is the same as that of the base emitter of the transistor Tr.

Switching by the transistor Tr is performed via a series resonant circuit of a capacitor C0 and an inductor L based on the output of the control winding N2.
The base current that is about to flow at the end of the OFF period is bypassed by the capacitor C3 and diode D3 of the snubber circuit until the ON period begins, so that the whisker-shaped Ic1 as shown in the third diagram does not flow. Further, at turn-off, since the capacitor C3 and the resistor R3 have relatively high impedance, the charge is drawn out smoothly between the base and the emitter, and the fall is good without Ic2 flowing as shown in the third diagram. Furthermore, since the energy remaining in the inductor L immediately after turn-off is damped by the capacitor C3 and the resistor R3 of the snubber circuit, there is no need to connect the damping resistor Rd in parallel to the inductor L as shown in the third diagram.

(Effects of the Invention) As described above, the present invention includes a series resonant circuit inserted between the base of the transistor and the control winding, and a capacitor connected in series between the base and emitter of the transistor. A snubber circuit consisting of a resistor and a diode in parallel with the resistor is connected so that the polarity of the diode is the same as that of the base and emitter of the transistor, so that the turn-off characteristics of the transistor are not deteriorated, as shown in Figure 3. It is possible to reduce the switching loss of the transistor by preventing the occurrence of the rising whisker-like Ic1. Therefore, the temperature of the transistor can be lowered and reliability and efficiency can be increased.
Moreover, since the capacitor and resistor of the snubber circuit also serve as damping of the energy accumulated in the inductor of the series resonant circuit, the number of parts can be reduced and the device can be provided at low cost.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the present invention, FIG. 2 shows a conventional example, and FIG. 3 shows voltage and current waveforms of a transistor. N1: Input winding, N2: Control winding, T: Transformer, Tr: Transistor, L: Inductor, C
0: Capacitor, C3, R3, D3: Snubber circuit.

Claims (1)

[Scope of Claims] 1. A transformer having an input winding and a control winding; the output of the control winding of this transformer is applied between the base and emitter to control on/off, and the input to the input winding is controlled. a series resonant circuit of an inductor and a capacitor inserted in a control output supply circuit to the base and emitter of the transistor by the control winding; a capacitor and a diode connected in series with each other and a series resonant circuit connected to the diode; A transistor inverter comprising: a snubber circuit having a resistor connected thereto and provided between the base and emitter of the transistor so that the polarity of the diode is the same as that of the base and emitter of the transistor. Device.